Tall red flowered Pea Plant crossed to dwarf white flowered plant yields only tall red flowered plants. A test cross shall give a ratio of

Options

A. `1:1`
B. `3:1`
C. `1:1:1:1`
D. `1:2:4:6:4:2:1`

Answer

To solve the question regarding the test cross of a tall red-flowered pea plant crossed with a dwarf white-flowered plant, we need to follow these steps:

### Step 1: Identify the Genotypes of the Parent Plants
- The tall red-flowered pea plant is dominant for both traits (height and flower color). We can denote its genotype as **TTRR** (homozygous dominant).
- The dwarf white-flowered plant is recessive for both traits. Its genotype can be denoted as **ttrr** (homozygous recessive).

### Step 2: Determine the F1 Generation
- When we cross the tall red-flowered plant (TTRR) with the dwarf white-flowered plant (ttrr), all offspring (F1 generation) will inherit one allele from each parent. Therefore, the F1 genotype will be **TtRr** (heterozygous for both traits).
- The phenotype of the F1 generation will be tall and red-flowered since both traits are dominant.

### Step 3: Perform a Test Cross
- A test cross involves crossing the F1 individual (TtRr) with a homozygous recessive individual (ttrr).
- The gametes produced by the F1 plant (TtRr) can be:
- TR (Tall, Red)
- Tr (Tall, White)
- tR (Dwarf, Red)
- tr (Dwarf, White)

- The gametes produced by the recessive parent (ttrr) will only be:
- tr (Dwarf, White)

### Step 4: Analyze the Offspring of the Test Cross
- When we perform the test cross, we can combine the gametes from the F1 plant with those from the recessive parent:
1. TR (from TtRr) with tr (from ttrr) → TtRr (Tall, Red)
2. Tr (from TtRr) with tr (from ttrr) → Ttrr (Tall, White)
3. tR (from TtRr) with tr (from ttrr) → ttRr (Dwarf, Red)
4. tr (from TtRr) with tr (from ttrr) → ttrr (Dwarf, White)

### Step 5: Determine the Phenotypic Ratio
- From the combinations above, we can see the phenotypes produced:
- Tall Red (TtRr)
- Tall White (Ttrr)
- Dwarf Red (ttRr)
- Dwarf White (ttrr)

- The resulting phenotypic ratio from the test cross is:
- 1 Tall Red : 1 Tall White : 1 Dwarf Red : 1 Dwarf White
- This gives us a ratio of **1:1:1:1**.

### Final Answer
The test cross will yield a phenotypic ratio of **1:1:1:1**.

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